Peritoneal carcinomatosis from an unknown primary site. Management of 15 patients

Peritoneal carcinomatosis from an unknown primary site is a rare and ill-defined entity. This work attempts to identify clinical and pathological features of patients with this disease and report the results of an aggressive combined treatment modality.

Retrospective analysis was performed of medical records of 15 patients with peritoneal carcinomatosis with no primary site identified at a single institution between 1989 and 2000. A primary gastrointestinal cancer was ruled out after a thorough endoscopic and radiologic work-up and complete exploratory surgery.

Four women and 11 men were identified; the average age was 49 years. All patients had cytoreductive surgery with peritonectomies; 4 patients underwent a second-look operation. Perioperative intraperitoneal chemotherapy was given to 10 of the 15 patients, and 9 patients received post-cytoreduction chemotherapy given intraperitoneally (1), systemically (7) or both intraperitoneally and systemically (1). Overall median survival from diagnosis was 19.0 months; 1 patient is alive with disease at 21 months; and 3 patients are disease-free at 17, 38, and 60 months from diagnosis. Significant positive predictive factors for survival were a small volume of ascites (P = 0.02), a large number of peritonectomies performed (P = 0.001), second-look cytoreduction (P = 0.003), perioperative intraperitoneal chemotherapy (P = 0.008) and postoperative chemotherapy (P= 0.01), either intraperitoneal or systemic.

Peritoneal carcinomatosis from an unknown primary site is a rare subset of primary peritoneal malignancy. Aggressive treatment may provide prolonged palliation with occasional long-term survival.